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The concept that HIV causes AIDS only by directly killing CD4 cells has been questioned by a number of investigators. There has been experimental support for a number of indirect mechanisms such as apoptosis, anergy, superantigen-induced cell proliferation and depletion, defective signaling, molecular mimicry, and autoimmunity. In this article we review the available evidence in support of these theories and suggest that in spite of their apparent differences, signaling by HIV through the T cell receptor could initiate the markedly different responses of activation, anergy, and apoptosis. However, the unifying mechanism as to how this is achieved remains unclear. It is likely that more than one of these mechanisms are involved in CD4 cell depletion during different phases of the disease. Understanding these mechanisms and their role in HIV pathogenesis would be important in new vaccine and therapeutic approaches.

Stiff person syndrome (SPS) is a rare, neurological disorder characterized by sudden cramps and spasms. High titers of enzyme-inhibiting IgG autoantibodies against the 65 kD isoform of glutamic acid decarboxylase (GAD65) are a hallmark of SPS, implicating an autoimmune component in the pathology of the syndrome. Studying the B cell compartment and the anti-GAD65 B cell response in two monozygotic twins suffering from SPS, who were treated with the B cell-depleting monoclonal anti-CD20 antibody rituximab, we found that the humoral autoimmune response in SPS is composed of a rituximab-sensitive part that is rapidly cleared after treatment, and a rituximab-resistant component, which persists and acts as a reservoir for autoantibodies inhibiting GAD65 enzyme activity. Our data show that these potentially pathogenic anti-GAD65 autoantibodies are secreted by long-lived plasma cells, which may either be persistent or develop from rituximab-resistant memory B lymphocytes. Both subsets represent only a fraction of anti-GAD65 autoantibody secreting cells. Therefore, the identification and targeting of this compartment is a key factor for successful treatment planning of SPS and of similar autoimmune diseases.

Background Dendritic cells (DCs) are professional antigen-presenting cells that form cellular networks surveying for pathogens and providing the first immunological barrier to the external environment. The fate of DCs is dependent on a cross-talk with NK cells that may lead to DC’s killing (editing) which is believed to keep in check their quality and quantity. Considering that HIV-1-infected DCs may become persistent viral reservoirs, we addressed the question of NK’ sr ole in infected DC’s elimination as well as the mechanisms involved. Methods Immature DCs (iDCs) were derived from CD14+ monocytes cultured for 6 days in the presence of IL-4 and GM-CSF. iDCs were infected with R5-HIV-1BAL (DCHIV). 24 h cocultures with autologous purified activated NK cells (aNK) were performed and DC’s apoptosis was analyzed by multiparametric flow cytometry, combining 7-AAD staining with the detection of death/survival molecules. Gene array analyses were performed to detect variations in gene expression between different coculture conditions. siRNA magnetofection was performed to silence c-FLIP and c-IAP2 anti-apoptotic genes’ expression in DCs. Live video microscopy was used to dissect apoptotic events during aNK-iDC contact. Results We show that, while iDCs were susceptible to NK editing, involving TRAIL/DR4 and not the perforin-pathway, DCHIV were resistant to NK-dependent cytotoxicity. We report that NK cells induce in DCHIV a dramatic increase in the expression of two anti-apoptotic molecules, c-FLIP and c-IAP2, responsible for the resistance of DCHIV to TRAIL-induced apoptosis. Moreover, we found that HMGB1, a key mediator of NK-DC crosstalk, is responsible for the upregulation of these two inhibitors. The consequence of the escape of DCHIV from NK cytotoxicity is an HMGB1-dependent increase in HIV replication in DCs, which is mediated by HMGB1. Discussion These observations show that under physiological conditions, the editing process of iDCs by NK cells occurs through rapid induction of TRAIL apoptosis in iDCs. Following HIV infection of DCs, NK cells increase DCs’ survival through an HMGB1-dependant mechanism inducing c-IAP2 and c-FLIP upregulation. This study provides new insights into how HIV hijacks DCs and uses the NK-DC crosstalk to maintain viability of longterm reservoirs, and it identifies potential therapeutic targets to eliminate infected DCs.

Peripheral B cells from six patients affected with the hyper-IgM immunodeficiency syndrome, characterized by an absence of IgG and IgA in serum with a concomitant elevated level of IgM, were analyzed for phenotypic and functional characteristics. We report that although the membrane antigenic pattern expression was characteristic of mature B cells, B cells from most patients exhibited an impairment in their in vitro response to several lymphokines, such as recombinant interleukin 2 (rIL-2) and low molecular weight B-cell growth factor (BCGF), that induce proliferation of anti-mu-activated B cells. This impairment was also found in response to a lymphokine mixture from a CD2-activated T-cell clone. The decrease in lymphokine-induced B-cell proliferation was accompanied by a low B-cell differentiation, whether patients' B cells were stimulated by the T-cell clone supernatant or rIL-2 and rIL6, lymphokines able to support differentiation of Staphylococcus aureus Cowan I (SAC)-activated B cells. In addition, none of the lymphokines tested were able to induce patients' B cells to switch from IgM-secreting cells to IgG- and IgA-secreting cells. We conclude that this syndrome is associated with a defect in lymphokine-dependent maturation of B lymphocytes, although the T- or the B-cell origin of the defect still cannot be determined.

Background Eosinophils are effector cells during parasitic infections and allergic responses. However, their contribution to innate immunity has been only recently unravelled.

We have previously reported that ex vivo retroviraly-mediated gc gene transfer into CD34 (+) bone marrow precursor cells led to the correction of the immunodeficiency in 9 out of 10 patients with X-linked severe combined immunodeficiency. Follow-up now reaches more that 6 years for the first 2 treated patients. Patients’immune function has been restored. The distribution of both TCR Vb family usage and TCR Vb CDR3 length still reveals a broadly diversified T cell repertoire. Moreover 6 years after treatment the thymus is still seeded by transduced progenitor cells as attested by the presence of TRECS in peripheral blood RTE. Among these patients, three (P4, P5 and P10) developed at 30 to 34 months after gene therapy a monoclonal T cell proliferation requiring a chemotherapy. P4 received also an allogenic HSCT from a MUD but died 26 months after the occurence of the lymphoproliferation. For P5 and P10, chemotherapy has led to an overall control of the clonal proliferation. These two patients are doing well and P5 is off treatment with a good immunological recovery. Genetic analysis of the blastic cells showed that in the two first cases the vector had integrated within or upstream of the LMO2 locus causing an insertional activation of LMO2 transcription. The last case revealed the involvement of several targeted sites, but their exact contribution to the lymphoproliferation is still under investigation. The repeated involvment of LMO2 as a site of vector integration in the proliferating T-cells points to an insertional activation of this gene as at least one of the causes of the oncogenic process. However, the long latency observed in all cases (> 30 months) suggests that additional “hits” have been required for overt desease. Synergy with gc expression and thereby induced proliferative signals (explaining occurrence in SCID-X1 patients only) is the most obvious hypothesis which we are trying to analyse in a mouse model. A deep analysis of retroviral integration patterns has been performed on patients’PBMCS by LAM-PCR to estimate the frequency of potentially harmful integration events and to assess the risk factors associated with the LTR’s strong enhancer effect of the MLV-based retroviral vector. 708 unique integration sites (IS) have been obtained from all analysed patients post-gene therapy and among them, 577 could be mapped unequivocally to the human genome. *Most of these insertions (63%) are located in the vicinity of 10kb or within the coding sequence of a known gene*. A significant peak of insertion frequency is related closely to the transcription strart site *among the 577 IS, 43 are common integration sites. Among the latter, we found out a high selection of genes involved in human oncogenic process.

We described in this paper the characteristics of a syngeneic anti-idiotypic serum made in BALB/c against BALB/c anti-poly (Glu 60 Ala 30 Tyr 10 ) (GAT) antibodies. This serum recognizes idiotypic determinants present in all anti-GAT sera whatever the allotypic markers of the mice used to prepare the sera. The functional effect of this serum on two helper cell lines is also described. Cell line BDF 1 /52 was obtained from GAT immunized lymph node cells (LNC). Cell line BDF 1 /E 3 was selected from splenic T-cells educated in vitro on GAT-pulsed adherent cells. Both lines were propagated in presence of filler cells, antigen, and medium containing T-cell growth factor(s) from splenic cells activated with concanavalin A. Both cell lines exhibit a helper activity as measured by the plaque-forming cell (PFC) response they induce in vitro in the presence of DNP-GAT and DNP sensitized B cells. Their helper activity is specific and they require a hapten-carrier bridge to activate B cells. These lines are able to induce IgG 1 , IgG 2a and IgG 2b anti-TNP PFC. Syngeneic anti-idiotypic serum B 658 inhibits specifically the function of these two lines but does not affect the helper activity of an OVA-specific T-cell line. The blocking activity of the serum can be adsorbed on a hybridoma protein with anti-GAT activity. This inhibition affects more dramatically the IgG 1 response than the IgG 2a and IgG 2b responses.

The supernatant of the T helper cell clone 52.3 (52.3-SN) was shown to induce polyclonal activation of resting B cells. 52.3-SN acts on most small B cells and through the allogeneic barrier. This supernatant induces cell size increase, RNA and DNA synthesis, and appearance of interleukin-2 and transferrin receptor. These results are interpreted as indicating the existence of a B Cell Activating Factor (BCAF) acting on resting B cells in an MHC-unrestricted way.TH cells can be obtained in an intermediate state of activation where they secrete lymphokines leading to B cell proliferation and not the biological activities leading to plasmocyte development. TH cell clones can induce sIgG− and sIgA− unprimed B cells to switch and express all classes and subclasses of immunoglobulin. The bulk of the response consists of IgM. Among the non IgM isotypes, IgG1 and IgA predominate. The supernatants prepared from TH cells reproduce these effects.

Two different monoclonal anti-idiotypic (Id) antibodies, HP-Id20 and HP-Id22, recognizing two discrete idiotopes characteristic of the anti-poly(Glu60 Ala30 Tyr10) (GAT) response were used to immunize BALB/c (GAT-responder) and DBA/1 (GAT-nonresponder) mice. The monoclonals were injected either copolymerized with keyhole limpet haemocyanin or polymerized with glutaraldehyde. The specific response was studied by two assays: (a) inhibition of binding of monoclonal anti-GAT antibody G5Bb2-2 to HP-Id20 and HP-Id22 and (b) GAT binding assays. In BALB/c GAT-responder mice, HP-Id20 and HP-Id22 immunization led to the preferential stimulation of immunoglobulin idiotypically related to anti-GAT antibodies (Ab1') and expressing anti-GAT activity. The results obtained with BALB/c nu/nu mice indicated that this response is T-cell-dependent. By means of the same experimental protocol GAT-nonresponder animals could be induced to produce anti-GAT antibodies after HP-Id immunization. This last result indicates that anti-Id immunization can bypass Ir gene control and does not preferentially stimulate the induction of GAT-specific T suppressor cells.

CD8+ T cells may play a beneficial role in human immunodeficiency virus (HIV)-infected patients by two mechanisms: HIV-specific cytotoxic activity and secretion of a soluble mediator(s) that inhibits HIV replication in vitro. Here we characterized both activities mediated by an HIV p24 gag -specific cytotoxic T lymphocyte (CTL) CD8+ clone derived from an HIV-infected patient. When the CTL clone was mixed with HIV-infected autologous CD4+ T cells, viral replication was suppressed. This viral inhibition was observed in heterologous CD4+ T cells and when CD8+ and CD4+ populations were separated by a semipermeable membrane, demonstrating the involvement of a diffusible factor(s). The lysis of autologous HIV-infected T cells was also detected. However, HIV suppression was more efficient when CD4+ and CD8+ T cells shared major histocompatibility complex alleles and were in direct contact. Thus, one and the same CD8+ T cell population can mediate both lysis of HIV-infected targets and nonlytic suppression of HIV replication. These results underline the multiple roles of CD8+ T lymphocytes in the suppression of HIV-infected cells.

The fine specificity of anti-Glu60Ala30Tyr10 (GAT) and anti-Glu60Ala40 (GA) proliferating cells was studied. T cells primed with GAT proliferate both to GAT and GA and GA-primed T cells proliferate also to GA and GAT. This cross-reactivity was unexpected given the results previously reported on the fine specificity of anti-GAT antibodies. The effect on the proliferation of BALB/c lymph node cells (LNC) of a syngeneic anti-idiotypic serum, prepared in BALB/c against anti-GAT antibodies, was studied. Two major points are made in this paper: (i) the in vitro addition of the anti-idiotypic serum in cultures containing GAT-primed LNC and GAT enhances the proliferation of GAT-specific T cells; (ii) the anti-idiotypic serum is effective in priming in vivo LNC which then acquire the capacity to proliferate specifically with GAT in vitro. These results further confirm the existence of idiotype-like determinants on T cells.

Eight monoclonal anti-idiotypic antibodies directed against public idiotopes have been further characterized: (a) they bind to public idiotopes with a high affinity; (b) they recognize all anti-poly(Glu60, Ala30, Tyr10) (GAT) antibodies as measured by inhibition of the anti-GAT plaque-forming cell response. This has been verified in three strains of mice. These reagents were not able to detect idiotope expression on eight GAT-specific helper T cell lines and clones. This result was obtained by two techniques: (a) idiotope expression at the T cell surface was measured by indirect immunofluorescence using a cell sorter with surface antigens H-2D, Thy-1.2, Lyt-1 and L3T4 as positive controls; (b) after immunoadsorption of [35S]methionine-labeled cellular extracts from two lines, no unique molecule was retained by the HP-idp22 monoclonal anti-idiotypic antibody coupled to Sepharose. Despite these negative results, this antibody was found to prime lymph node cells in vivo, which were able to proliferate specifically in response to GAT. Two T cell lines derived from this lymphocyte population do not express any of the idiotopes tested. These results suggest that monoclonal anti-idiotypic antibodies may be influencing T lymphocyte activity indirectly.

The effects of helper T-cell clone supernatants on resting human B cells were investigated. Four different helper T-cell clones (two T4+ and two T8+) were stimulated by anti-T3 monoclonal antibodies on Sepharose beads or anti-T11(2) plus anti-T11(3) monoclonal antibodies. The supernatants from these activated clones induced the proliferation of highly purified resting B lymphocytes from the peripheral blood. The B cells exhibited a cell size and a surface-antigen pattern (4F2 antigen and transferrin receptor) of phase G0 B cells, and they were functionally resting. In response to T-cell supernatants a large fraction of the B cells enlarged and expressed 4F2 antigens and transferrin receptors. In gel filtration, the corresponding activity migrated with an apparent Mr of 12,000-15,000. Our findings strongly support the existence of a human B-cell-activating factor acting on resting B cells and causing them to enter phase G1 of the cell cycle.

Recognition by specific T helper (T h ) cells of antigen presented by antigen-presenting cells (APC) involves, in addition to the antigen-specific receptor, non-antigen-specific molecules such as L3T4 and LFA1. In the present study, we analyzed the relationship between the avidity for antigen presented by APC of three T h cell lines and the participation of L3T4 and LFA1 cell surface antigens. We found a correlation between the avidity of T h cells for the complex GAT/Ia on APC measured by two independent assays and the participation of the cell-adhesion molecules L3T4 as measured by the ability of corresponding monoclonal antibody (MAb) to block the antigen-induced proliferation of T h cells. In contrast to the situation found with cytolytic T-lymphocyte (CTL) clones, we also found a differential inhibiting effect of anti-LFA1 MAb on the GAT-specific proliferation of the three T h clones. The results indicate a direct correlation between the inhibitory effects of anti-LFA1 and anti-L3T4 MAb and the affinity of T h cells for the complex formed by antigen and Ia.

A substantial amount of work has been accumulated trying to understand the cellular basis for the Ir gene control of the immune response to the synthetic polymer (Glu60 Ala30 Tyr10) (GAT). Conflicting data has been published. Yano et al. (1) suggested that the defect of nonresponder (NR) animals bearing H-2q and H-2S haplotype was the incapacity of their antigen presenting cells (APC) to present GAT to T cells. On the contrary Araneo et al.(2) showed that NR APC can present antigen to lymph nodes (LN) T cells from (responder x nonresponder) animals (R x NR) F1. Using a different approach Kapp et al. (3) have shown the selective induction of T suppressor (TS) cells in GAT NR animals. These TS cells inhibit the anti-GAT response induced by immunizing NR animals with GAT complexed to methylated serum albumin (GAT-MBSA). The mechanism by which GAT-MBSA induces an anti-GAT response in NR animals is not understood : some GAT specific T helper (TH) cells are induced but contrary to GAT specific TH cells from R animals these cells cannot generate anti-GAT response in presence of soluble GAT (4). Nothing is known about the capacity of soluble GAT to induce helper T cells in nonresponder animals.

International audience; Data on the efficacy and safety of seasonal influenza vaccines in patients with inflammatory bowel disease (IBD) remain scarce. The aim of the study was to evaluate the impact of immunosuppressive (IS) therapeutics on serological response to 2-year influenza vaccination in IBD adults. A multicentre prospective study performed in 255 IBD adults (18-64 years) receiving the trivalent influenza vaccine in the years 2009-2010 and 2010-2011. Haemagglutination inhibition (HI) titres were assessed before and 3 weeks and 6 months after vaccination. At inclusion, 31 patients were receiving no IS treatment (Group A), 77 were receiving IS treatment without anti-TNF (Group B) and 117 were receiving anti-tumour necrosis factor (TNF) treatment with or without IS treatment (Group C). Three weeks after the first vaccination, rates of seroprotection were 77, 75 and 66% for strain A/H1N12007 (p = 0.35), 77, 68 and 52% for strain A/H3N2 (p = 0.014) and 97, 96 and 95% for strain B (p = 0.99) in Groups A, B and C, respectively. Seroconversion rates for A/H1N12007 (67, 64 and 54%; p = 0.28), A/H3N2 (63, 50 and 41%; p = 0.074) and strain B (63, 76 and 60%; p = 0.078) were not significantly different among treatment groups. At 6 months after vaccination, seroprotection rates were lower in Group C compared with Groups A and B. Comparable results were observed for the second year of vaccination. No impact on Harvey-Bradshaw and Mayo scores was detected. Influenza vaccine yielded high seroprotection rates in IBD patients. Persistence of seroprotection was lower in patients with anti-TNF treatment. ClinicalTrials.gov, number NCT01022749.

At an early stage of HIV-1 transmission, plasmacytoid dendritic cells (pDCs) and natural killer (NK) cells are recruited into mucosal tissues. pDCs are the major source of type I interferon (IFN-α), a powerful innate antiviral cytokine, and a strong pDC response is associated with spontaneous virus control. The contribution of pDCs to licensing NK cells and inducing antiviral immunity make them a key player in the early phase of HIV-1 infection. In contrast, the chronic expression of IFN-α was found to be a key mediator for HIV pathogenesis. We addressed herein the question of the molecular mechanisms involved in the generation of Interferon-producing Killer pDCs (IKpDCs), and the consequences on viral control.

Zika virus (ZIKV) is an unprecedented epidemiological phenomenon which surprised the world. For many years, it was considered a trivial virus responsible for only a handful of human infections, self-limited and benign, in Africa and Southeast Asia. But then, after decades of silent spread, a first epidemic broke out in Micronesia in 2007 – like a warning signal. A few years later, a sudden Zika outbreak of larger scale occurred in the Pacific islands before reaching Brazil in 2015. During this period, Zika was associated with severe neurological complications, highlighting its serious pathogenic potential for humans. Since its emergence, more than 80 countries and territories have been affected by the ZIKV pandemic, which is now recognized as a neurotropic and teratogenic virus. The association of contemporary ZIKV strains with severe forms of disease in humans, that have never been reported before, has raised the hypothesis of newly acquired pathogenicity. In this regard, my doctoral research aimed to determine whether the scope of the current epidemic was partly facilitated by viral factors that improved ZIKV fitness. To this end, my research project focused on the identification of the viral molecular factors involved in Zika virus pathogenicity in humans based on the development of molecular clones., Le virus Zika (ZIKV) est un phénomène épidémiologique sans précédent qui surprit le monde entier. Pendant de nombreuses années, il fut considéré comme un virus anodin responsable d’une poignée d’infections humaines, auto-limitées et bénignes, en Afrique et en Asie du Sud-est. Mais, après des décennies de propagation silencieuse, une première épidémie éclata en Micronésie en 2007 - tel un signal d'alarme. Quelques années plus tard, une soudaine épidémie de ZIKV de plus grande ampleur se déclara dans les îles du Pacifique avant d'atteindre le Brésil en 2015. Au cours de cette période, Zika fut associé à de graves complications neurologiques, mettant en évidence son fort potentiel pathogène pour l'homme. Depuis son émergence, plus de 80 pays et territoires ont été touchés par la pandémie de ZIKV, désormais reconnu comme un virus neurotrope et tératogène. L'association des souches contemporaines de ZIKV à des formes graves de maladie chez l'homme, qui n'ont jamais été signalées auparavant, a soulevé l'hypothèse d'une pathogénicité nouvellement acquise. Ainsi, mes travaux de doctorat visaient à déterminer si l'ampleur de l'épidémie actuelle pouvait en partie avoir été facilitée par des facteurs viraux qui auraient renforcé la fitness du ZIKV. À cette fin, mon projet de recherche s'est concentré sur l'identification des facteurs moléculaires viraux impliqués dans la pathogénicité du virus Zika chez l’homme à partir du développement de clones moléculaires.

This work suggests that increased apoptosis limits the virus-driven expansion of TNFa T cells during untreated infection, but that the rapid suppression of apoptosis following antiretroviral therapy favours a pro-inflammatory polarisation of T cells, which could be a risk factor for metabolic and inflammatory side-effects associated to immune restoration.; Ce travail suggère que l'apotose régule différentiellement la demi-vie des populations lymphocytaires T productrices de cytokines. Processus anti-inflammatoire physiologique, l'apoptose exerce principalement son contrôle négatif sur les cellules T productrices de TNFa. Lors des traitements anti-rétroviraux combinés, la réduction de l'apoptose lymphocytaire est associée à une polarisation pro-inflammatoire qui pourrait favoriser la constitution des anomalies métaboliques mais aussi la survenue des pathologies inflammatoires associées à la restauration immunitaire.